1. Field of the Invention
This invention relates to a manufacturing apparatus and method for amorphous alloy.
2. Description of the Related Art
Recently, amorphous alloys having very low critical cooling rates of 1 to 100 K/s have been developed. These are, for example, amorphous alloys of Zr--Al--Co--Ni--Cu system, Zr--Ti--Al--Ni--Cu system, Zr--Ti--Nb--Al--Ni--Cu system, Zr--Ti--Hf--Al--Co--Ni--Cu system, Zr--Al--Ni--Cu system, etc. Among these alloys, Zr--Al--Ni--Cu system is regarded as especially preferable. And, accompanying these alloys, large (bulk) molded products of amorphous alloy are being produced with various methods. These methods are, for example, forging method in which molten metal is pressed and formed into a predetermined configuration, rolling method in which molten metal is rolled, and casting method in which molten metal is casted into a predetermined configuration.
In the above forging method and rolling method, for example, metal material is placed on a portion for fusing formed on a water-cooled copper mold, fused by arc discharge, etc., and, molten metal having a predetermined configuration on the mold is spread by an upper mold or filled into the mold (rolled) with a (forging) roll, and cooled over a critical cooling rate to form amorphous alloy. In these forging method and rolling method, contact pressure of the molten metal and the mold is high in comparison with the casting method for process of pushing the molten metal to the mold, very high cooling rate is obtained for high heat conductivity on contact portion, and good large (bulk) molded product of amorphous alloy having high super cooling degree is obtained.
However, to obtain better large (bulk) molded product of amorphous alloy, there are problems as follows.
1 Although time between the fusing process and the pressing process has to be as short as possible because the forming has to be completed before the molten metal solidifies, heat of the molten metal is immediately absorbed by the mold when the arc discharge or electronic beam for fusing is stopped because the metal material is fused on the water-cooled copper mold, and temperature of the molten metal is rapidly decreased thereby.
2 Alloy (the metal material) to be fused on the part where the alloy contacts the mold can not be fused because the alloy is fused on the water-cooled copper mold. That is to say, to fuse the alloy to be fused entirely without fusing the mold, high-level temperature control with which the temperature of the mold is not increased over the melting point of the mold is necessary, and this is practically difficult.
3 Although heat contact between the mold and the alloy to be fused is relatively bad, it is impossible to completely fuse an alloy having a melting point higher than that of the material of the mold.
For the problems of 1, 2, and 3, the temperature of the molten metal can not be high. This is a disadvantage in the above described point "the forming has to be completed before the molten metal solidifies".
4 Further, in case that the alloy is not fused completely, clusters (small groups of atoms of which disposition is similar to that of crystal), which may become crystal nuclei, are discharged from surface of the non-fused portion touching the mold. In forming of amorphous by rapid cooling over the critical cooling rate, it is extremely inconvenient that the molten metal includes the clusters which may become crystal nuclei.
5 On the other hand, although the alloy to be fused can be completely fused, with a mold having high melting point such as a mold made of carbon, heat conductivity is insufficient to cool the molten metal over the critical cooling rate, when the molten metal is filled into the mold.
It is therefore an object of the present invention to provide a manufacturing apparatus and method for amorphous alloy with which a good and large (bulk) molded product of amorphous alloy can be obtained easily and certainly.